Kono Naka ni Hitori, Imouto ga Iru! is a romantic comedy anime series that follows Shougo Mikadono, a young man set to inherit his father's corporation. To do so, he must find a suitable wife during high school. However, one of his classmates is secretly his sister, complicating his quest for love. The show combines humor and mystery as Shougo navigates these challenges. It explores themes of family, identity, and romance.